Variable speed television



Feb. 22, 1938. A MCL. NICOLSON 2,109,339

VARIABLE SPEED TELEVISION Filed Feb. 8. 1954 :ELEr* l JR RECEIVER IAMPLIFIER Hulk-j INVENTOR Alexander MLean Nuznlsnn BY M/KQ ATTORN EYPatented Feb. 22, 1938 UNITED STATES PATENT OFFICE VARIABLE SPEEDTELEVISION Application February 8, 1934, Serial No. 710,229

'7 Claims.

This invention relates to the transmission of intelligence in the formof visible images with a rapidity suflicient to give the illusion ofmotion and particularly to such a system employing an. electrodynamicelectrical discharge or arc, which is propagated along a predeterminedpath and modulated in accordance with the light and shade densities ofan object or image being transmitted.

There are several different types of systems for the transmission ofimages, which fundamentally distinguish from one another on the basis ofthe method of and apparatus for propagating light beam over the objector screen used for observa-- tion. Such systems are well known. such asthe mirror drum, disc, cathode ray. and electrodynarnic arc systems, thelatter of which are disclosed in my United States Patents Nos.1,863,278.. issued June 14, 1932 and 1,839,696, issued January 5, 1932.The present are system differs from those disclosed in the patents bythe process known as modulation. In the patents the electrical dischargeor are is varied in intensity, while in the present invention,modulation occurs by varying the arc speed. Thus a dark spot is createdby a relatively high speed motion of the arc, while a bright spot isproduced by a relatively slow propagation thereof, the intermediateintensities being produced by intermediate spccds.

An object of the invention is to transmit and reproduce televisionimages.

Another object of the invention is to scan an object and reproduce theimages thereof with an eleetrodynamic discharge or are.

A further object of the invention is to reproduce television images witha moving electrical discharge or are whose rate of propagation is variedin accordance with the light and shade densities of the object or imagebeing transmitted. this variation reproducing the image or object.

It is well known that the eye integrates light, within certain limits,similar to that of a photographic film. That is, should light of adefinite iz'atensity be projected on the eye within definite timelimits, this light will appear brighter. the longer the projection. Wehave, therefore, a method of modulating a constant intensity light beamto reproduce a television image.

As disclosed in the above-mentioned patents, the electrical discharge ispropagated along electrode rails over a definite area. These electroderails are provided with a source of voltage to produce the arc.Surrounding the electrode rails is a magnetic field which provides aforce on the discharge for propagating it along the rails. If the arclength, the electrode voltage and the field strength are maintainedconstant, the arc will have a constant speed of propagation. Should thefield, however, be varied, the speed will also vary correspondingly.

The invention will be more fully understood by reference to thefollowing description read in conjunction with the accompanying drawingin which:

Fig. 1 is a diagrammatic representation of transmitter terminalapparatus, and

Fig. 2 is a similar representation of the receiver apparatus involvingthe invention.

In Fig. 1 an electrodynamic arc screen. similar to those disclosed inthe abovementioned patents. comprises electrode rails 5 and i, a fieldwinding 1, which represents a solenoid or other type of coil of manyturns, and a mask 8 with a pinhole or lens 9 therein. The electroderails 5 and l are energized from a source of direct current potential l2under control of a rheostat 13, while the field winding 1 is suppliedfrom a source of potential I4 under control 01 a rheostat :5. In thislast-mentioned supply circuit is a secondary of a transformer H, theprimary of which is com nected to an amplifier Hi. This amplifierreceives its input from a photosensitive device 19 posi tioned in theneighborhood of the screen to reccive light variations corresponding tothe light and shade densities of an object, such as ll. which isexplored with the light beam from the arc screen. The amplifier l8 feedsa transmitter 2! for transmission from an antenna 2 or over wiresconnected at 23.

The above transmitter operates in a simple manner. An electricaldischarge is produced across the electrodes 5 and 6 from the potentialsource I2 and propagated therealong by the field produced from thesource 14. the respective rheostats being adjusted to provide the speedoi prop section which is required to produce the images at a sufficientrate of speed to produce the illusion of motion. As the arc travelsalong its rails. light therefrom scans the object ll and electricalcurrents will be set up in the device H), which after a predeterminedamount of amplification are impressed upon the transmitter 2|. A portionof the energy from the amplifier i8, however, is returned to the field Ifor the purpose of synchronizing the electrical discharge on the rails 5and 6 at the transmitter. This synchronizing system is in accordancewith the disclosure in copending application Serial No. 584,797, filedJan-- uary 5, 1932.

Referring now to the receiver in Fig. 2, the transmitted impulses arereceived on an antenna 39 or over wire lines to terminals 3| andimpressed upon a receiver 32. The detected currents are then amplifiedin amplifier 34 and impressed upon an output transformer 35. An aresystem similar to the one in Fig. 1 is employed at the receiver, primenumerals being given to elements corresponding to those in Fig. 1. Nowthe incoming impulses impressed on the transformer 35 vary the fieldexcitation in accordance with the light and shade densities of theobject 0 and thus produce a variation in the rate of propagation of theare along the electrode rails 5 and 6 to produce the image of the objectbeing scanned. A similar variation is set up in the transmitter screen,thus producing the synchronism desired. It is to be understood that therheostats l3 and I5 must be set to produce substantially the samepropagation at the receiver as at the transmitter. Also that thesynchronizing variations may have smaller amplitudes than the modulatingvariations but the proportionalities between them must remainsubstantially constant. The mask 8 in Fig. 2 may be a ground glassthrough which the image is viewed directly, or it may have a pinhole orlens similar to that in Fig. 1 and the light projected on a screen forobservation.

The above variable speed television system has several advantages oversimilar systems in which the arc current is varied to producemodulation. The present system requires a minimum of apparatus byeliminating certain synchronizing controls and permits of a greatervariation in the accuracy of spacing the electrodes to producetelevision transmission. There are other advantages in the use of such asystem in view of the fact that it requires no mechanically movingelements and is especially adapted for variable speed modulation.

What is claimed is:

1. In a television transmission system, the combination of means forproducing a primary light source having a constant intensity at alltimes, said light source comprising an ionized path, means for immersingsaid light source in a magnetic field for moving said source, means forprojecting the light from said source to an object to be scanned, meansfor translating the light from said object into electrical currents,means for transmitting said currents to receiving app-arat-us, means atsaid receiving apparatus for immersing a second light source similar tosaid first light source in a magnetic field, said second light sourcehaving a constant intensity at all times, and means for impressing saidreceived currents on said immersing means for varying the speed of saidlight source in accordance with the light and shade densities of saidobject being scanned by the transmitter.

2. In a television system, a combination of a transmitter and areceiver, a plurality of electrode rails at said transmitter supplied bya constant voltage to produce a constant electrical dischargetherebetween at all times, means for creating a field in which saiddischarge is located, means for scanning an object with the light fromsaid discharge, means for translating said light variations intoelectrical currents, means for transmitting said currents to receivingapparatus comprising a similar electrical discharge system havingsimilar electrode rails and means for creating a field, and means forvarying the energy supplied to both of said field creating means forvarying the speed of said discharges in accordance with the light andshade densities of said object, the intensity of said dischargesremaining constant at all times.

3. In a radio receiving system, a receiving apparatus comprising aplurality of electrodes arranged to form a field of view, a constantenergy supply for producing a constant intensity discharge at all timesbetween said electrodes and in a single plane, a field winding producinga field in which said discharge is positioned, an energy supply for saidwinding, and means for varying said last mentioned energy supply inaccordance with the light and shade densities of an image or object,said means including a feed back circuit connected to said fieldwinding.

4. In a radio receiving system, means for receiving electrical currentscorresponding to light and shade densities of an object, a plurality ofelectrode rails, a source of energy having a constant value producing aconstant intensity discharge at all times between said rails, and in asingle plane, a field winding for producing a field in which saidelectrode rails are positioned, said :iield being supplied from aconstant source of energy, and means for varying the intensity of saidfield in accordance with the light and shade densities of an image orobject to be reproduced.

5. The method of television reception of the image of a scanned objectvisible with a constant intensity moving electrical discharge movable ina single plane in a magnetic field comprising varying the speed of saidmoving discharge by varying the strength of said magnetic field inaccordance with the light and shade densities of said scanned object toproduce dark elements by increasing the speed and producing lightelements by decreasing the speed of said discharge in properproportionalities, the absolute intensity of said discharge remainingconstant at all times.

6. The method of television transmission and reception of images of ascanned object with visible moving electrical discharges having constantintensities at all times, comprising scanning said object, obtainingelectrical currents characterized by the light and shade densities ofsaid object scanned with one constant intensity electrical discharge andvarying the speed of another moving electrical discharge having aconstant intensity in accordance with the currents produced with thefirst discharge while scanning, the absolute intensity of each of saiddischarges being maintained constant.

7. In a television receiving system, means for producing a primaryconstant intensity light source, said light source comprising an ionizedpath, means tending to move said light source at a constant speed over acertain area in a single plane, and means for varying the speed of saidsource per unit area in accordance with the iight and shade variationsof an image to be reproduced while maintaining said light source at aconstant absolute intensity at all times.

ALEXANDER MCLEAN NICOLSON.

